23.1 Induced Emf and Magnetic Flux

23.1 Induced Emf and Magnetic Flux

  • This butterfly has inherent symmetries.
  • There is a hint of symmetry between magnetism and electricity found in the preceding chapter.
  • We know that a current creates a magnetic field.
    • A magnetic field can create a current if nature is symmetric.
    • The Hall effect is caused by a magnetic force.
    • That could cause a current.
    • The answer was found in an experiment.
    • The English and American scientists independently demonstrated that magnetic fields can produce currents after 12 years after Oersted's discovery.
  • Magnetic fields are essential to our technological society.
    • magnetism is used to generate current in the ubiquitous generator found in automobiles, on bicycles, nuclear power plants, and so on.
    • Other devices that use magnetism to induce currents include pickup coils in electric guitars, transformers of every size, certain microphones, airport security gates, and damping mechanisms on sensitive chemical balances.
    • The behavior of AC circuits depends on the effect of magnetic fields on currents.
  • When the switch is not in use, a magnetic field is produced in the top part of the iron ring and transmitted to the bottom part of the ring.
    • The galvanometer can be used to detect a current.
    • The galvanometer can detect a current in one direction when the switch is closed.
    • The galvanometer can detect a current in the opposite direction when the switch is open.
    • There is no current through the galvanometer when the switch is closed or open.
    • The current is caused by closing and opening the switch.
    • The current is created by the change in magnetic field.
    • The emf causes the current to flow.
    • If there is a path for current to flow, the current is a result of an emf caused by a changing magnetic field.
  • A magnetic field can produce a current.
    • A change in the field produced by the top coil causes an emf and a current in the bottom coil.
    • The galvanometer shows the currents in opposite directions when the switch is open and closed.
    • When the switch is closed or open, there is no current flowing through the galvanometer.
  • Emfs of opposite signs are reversed by reversing poles.
    • If the coil is moved it will produce the same results.
    • When the magnet is stationary relative to the coil, there is no emf.
  • emfs are produced by the movement of a magnet relative to a coil.
    • If the coil is moved relative to the magnet, the same emfs will be produced.
    • When there is no motion, the emf is zero if the speed is greater than the magnitude of the emf.
  • The alternating current emf is produced by a coil that rotates in a magnetic field.
  • The generator is very similar to a motor.
  • An emf can be produced by rotation of a coil.
    • The basic construction of a generator is turning the coil into electric energy.
    • The generator is very similar to a motor.
  • Changing the magnitude or direction of a magnetic field can produce an emf.
  • There are units of magnetic flux.